Barrier layer for correlated electron material

ABSTRACT

Subject matter disclosed herein may relate to correlated electron switch devices, and may relate more particularly to one or more barrier layers having various characteristics formed under and/or over and/or around correlated electron material.

BACKGROUND

Field

Subject matter disclosed herein may relate to correlated electron switchdevices, and may relate more particularly to one or more barrier layershaving various characteristics formed under and/or over and/or aroundcorrelated electron material.

Information

Integrated circuit devices, such as electronic switching devices, forexample, may be found in a wide range of electronic device types. Forexample, memory and/or logic devices may incorporate electronic switchesthat may be used in computers, digital cameras, cellular telephones,tablet devices, personal digital assistants, etc. Factors related toelectronic switching devices, such as may be incorporated in memoryand/or logic devices, that may be of interest to a designer inconsidering suitability for any particular application may includephysical size, storage density, operating voltages, impedance rangesand/or power consumption, for example. Other example factors that may beof interest to designers may include cost of manufacture, ease ofmanufacture, scalability, and/or reliability. Moreover, there appears tobe an ever increasing need for memory and/or logic devices that exhibitcharacteristics of lower power and/or higher speed.

BRIEF DESCRIPTION OF THE DRAWINGS

Claimed subject matter is particularly pointed out and distinctlyclaimed in the concluding portion of the specification. However, both asto organization and/or method of operation, together with objects,features, and/or advantages thereof, it may best be understood byreference to the following detailed description if read with theaccompanying drawings in which:

FIG. 1 shows block diagram of an example embodiment of a correlatedelectron switch device comprising a correlated electron material, inaccordance with an embodiment.

FIG. 2 shows a plot of current density versus voltage for a correlatedelectron switch, in according to an embodiment.

FIG. 3 is a schematic diagram of an equivalent circuit of a correlatedelectron switch, in accordance with an embodiment.

FIG. 4a depicts a simplified flowchart for an example process forfabricating correlated electron material devices, in accordance with anembodiment.

FIG. 4b depicts a simplified flowchart for an example process forfabricating correlated electron material devices, in accordance with anembodiment.

FIG. 4c depicts a simplified flowchart for an example process forfabricating correlated electron material devices, in accordance with anembodiment.

FIG. 5 is an illustration depicting a cross-sectional view of a portionof an example correlated electron material device, in accordance with anembodiment.

FIG. 6 is an illustration depicting a cross-sectional view of a portionof an example correlated electron material device including barrierlayers at least in part to prevent oxidation of one or more electrodesand/or prevent formation of a substantially non-conducting and/ornon-switching interface layer, in accordance with an embodiment.

FIG. 7 depicts a simplified flowchart for an example process forfabricating correlated electron material devices including one or morebarrier layers at least in part to prevent oxidation of one or moreelectrodes and/or prevent formation of a substantially non-conductingand/or non-switching interface layer, in accordance with an embodiment.

FIG. 8 is an illustration depicting a cross-sectional view of a portionof an example correlated electron material device, in accordance with anembodiment.

FIG. 9 is an illustration depicting a cross-sectional view of a portionof an example correlated electron material device including barrierlayers at least in part to prevent carbon diffusion from a correlatedelectron material, in accordance with an embodiment.

FIG. 10 is an illustration depicting a cross-sectional view of a portionof an example correlated electron material device including a conformalbarrier layer at least in part to prevent out diffusion from edges ofcorrelated electron material, in accordance with an embodiment.

FIG. 11 depicts a simplified flowchart for an example process forfabricating correlated electron material devices including one or morebarrier layers at least in part to prevent carbon diffusion from acorrelated electron material, in accordance with an embodiment.

Reference is made in the following detailed description to accompanyingdrawings, which form a part hereof, wherein like numerals may designatelike parts throughout that are corresponding and/or analogous. It willbe appreciated that the figures have not necessarily been drawn toscale, such as for simplicity and/or clarity of illustration. Forexample, dimensions of some aspects may be exaggerated relative toothers. Further, it is to be understood that other embodiments may beutilized. Furthermore, structural and/or other changes may be madewithout departing from claimed subject matter. References throughoutthis specification to “claimed subject matter” refer to subject matterintended to be covered by one or more claims, or any portion thereof,and are not necessarily intended to refer to a complete claim set, to aparticular combination of claim sets (e.g., method claims, apparatusclaims, etc.), or to a particular claim. It should also be noted thatdirections and/or references, for example, such as up, down, top,bottom, and so on, may be used to facilitate discussion of drawings andare not intended to restrict application of claimed subject matter.Therefore, the following detailed description is not to be taken tolimit claimed subject matter and/or equivalents.

DETAILED DESCRIPTION

References throughout this specification to one implementation, animplementation, one embodiment, an embodiment, and/or the like meansthat a particular feature, structure, characteristic, and/or the likedescribed in relation to a particular implementation and/or embodimentis included in at least one implementation and/or embodiment of claimedsubject matter. Thus, appearances of such phrases, for example, invarious places throughout this specification are not necessarilyintended to refer to the same implementation and/or embodiment or to anyone particular implementation and/or embodiment. Furthermore, it is tobe understood that particular features, structures, characteristics,and/or the like described are capable of being combined in various waysin one or more implementations and/or embodiments and, therefore, arewithin intended claim scope. In general, of course, as has always beenthe case for the specification of a patent application, these and otherissues have a potential to vary in a particular context of usage. Inother words, throughout the disclosure, particular context ofdescription and/or usage provides helpful guidance regarding reasonableinferences to be drawn; however, likewise, “in this context” in generalwithout further qualification refers to the context of the presentdisclosure.

Particular aspects of the present disclosure describe methods and/orprocesses for preparing and/or fabricating correlated electron materials(CEMs) to form a correlated electron switch, for example, such as may beutilized to form a correlated electron random access memory (CERAM) inmemory and/or logic devices, for example. Correlated electron materials,which may be utilized in the construction of CERAM devices and CEMswitches, for example, may also comprise a wide range of otherelectronic circuit types, such as, for example, memory controllers,memory arrays, filter circuits, data converters, optical instruments,phase locked loop circuits, microwave and millimeter wave transceivers,and so forth, although claimed subject matter is not limited in scope inthese respects. In this context, a CEM switch may exhibit asubstantially rapid conductor-to-insulator transition, which may bebrought about by electron correlations rather than solid statestructural phase changes, such as in response to a change from acrystalline to an amorphous state, for example, in a phase change memorydevice or, in another example, formation of filaments in conductive andresistive RAM devices. In one aspect, a substantially rapidconductor-to-insulator transition in a CEM device may be responsive to aquantum mechanical phenomenon, in contrast to melting/solidification orfilament formation, for example, in phase change and resistive RAMdevices. Such quantum mechanical transitions between relativelyconductive and relatively insulative states, and/or between first andsecond impedance states, for example, in a CEM may be understood in anyone of several aspects. As used herein, the terms “relatively conductivestate,” “relatively lower impedance state,” and/or “metal state” may beinterchangeable, and/or may, at times, be referred to as a “relativelyconductive/lower impedance state.” Similarly, the terms “relativelyinsulative state” and “relatively higher impedance state” may be usedinterchangeably herein, and/or may, at times, be referred to as arelatively “insulative/higher impedance state.”

In an aspect, a quantum mechanical transition of a correlated electronmaterial between a relatively insulative/higher impedance state and arelatively conductive/lower impedance state, wherein the relativelyconductive/lower impedance state is substantially dissimilar from theinsulated/higher impedance state, may be understood in terms of a Motttransition. In accordance with a Mott transition, a material may switchfrom a relatively insulative/higher impedance state to a relativelyconductive/lower impedance state if a Mott transition condition occurs.The Mott criteria may be defined by (n_(c))^(1/3) a≈0.26, wherein n_(c)denotes a concentration of electrons, and wherein “a” denotes the Bohrradius. If a threshold carrier concentration is achieved, such that theMott criteria is met, the Mott transition is believed to occur.Responsive to the Mott transition occurring, the state of a CEM devicechanges from a relatively higher resistance/higher capacitance state(e.g., an insulative/higher impedance state) to a relatively lowerresistance/lower capacitance state (e.g., a conductive/lower impedancestate) that is substantially dissimilar from the higherresistance/higher capacitance state.

In another aspect, the Mott transition may be controlled by alocalization of electrons. If carriers, such as electrons, for example,are localized, a strong coulomb interaction between the carriers isbelieved to split the bands of a CEM to bring about a relativelyinsulative (relatively higher impedance) state. If electrons are nolonger localized, a weak coulomb interaction may dominate, which maygive rise to a removal of band splitting, which may, in turn, bringabout a metal (conductive) band (relatively lower impedance state) thatis substantially dissimilar from the relatively higher impedance state.

Further, in an embodiment, switching from a relatively insulative/higherimpedance state to a substantially dissimilar and relativelyconductive/lower impedance state may bring about a change in capacitancein addition to a change in resistance. For example, a CEM device mayexhibit a variable resistance together with a property of variablecapacitance. In other words, impedance characteristics of a CEM devicemay include both resistive and capacitive components. For example, in ametal state, a CEM device may comprise a relatively low electric fieldthat may approach zero, and therefore may exhibit a substantially lowcapacitance, which may likewise approach zero.

Similarly, in a relatively insulative/higher impedance state, which maybe brought about by a higher density of bound or correlated electrons,an external electric field may be capable of penetrating a CEM and,therefore, a CEM may exhibit higher capacitance based, at least in part,on additional charges stored within a CEM. Thus, for example, atransition from a relatively insulative/higher impedance state to asubstantially dissimilar and relatively conductive/lower impedance statein a CEM device may result in changes in both resistance andcapacitance, at least in particular embodiments. Such a transition maybring about additional measurable phenomena, and claimed subject matteris not limited in this respect.

In an embodiment, a device formed from a CEM may exhibit switching ofimpedance states responsive to a Mott-transition in a majority of thevolume of a CEM comprising a device. In an embodiment, a CEM may form a“bulk switch.” As used herein, the term “bulk switch” refers to at leasta majority volume of a CEM switching a device's impedance state, such asin response to a Mott-transition. For example, in an embodiment,substantially all CEM of a device may switch from a relativelyinsulative/higher impedance state to a relatively conductive/lowerimpedance state or from a relatively conductive/lower impedance state toa relatively insulative/higher impedance state responsive to aMott-transition. In an embodiment, a CEM may comprise one or moretransition metals, one or more transition metal compounds, one or moretransition metal oxides (TMOs), one or more oxides comprising rare earthelements, one or more oxides of one or more f-block elements of theperiodic table, one or more rare earth transitional metal oxideperovskites, yttrium, and/or ytterbium, although claimed subject matteris not limited in scope in this respect. In an embodiment, a CEM devicemay comprise one or more materials selected from a group comprisingaluminum, cadmium, chromium, cobalt, copper, gold, iron, manganese,mercury, molybdenum, nickel, palladium, rhenium, ruthenium, silver, tin,titanium, vanadium, yttrium, and zinc (which may be linked to a cation,such as oxygen or other types of ligands), or combinations thereof,although claimed subject matter is not limited in scope in this respect.

FIG. 1 shows an example embodiment 100 of a CES device comprising CEM,such as one or more materials 102, sandwiched between conductiveterminals, such as conductive terminals 101 and 103. In an embodiment, aCES device, such as CES device 100, may comprise a variable impederdevice. As utilized herein, the terms “correlated electron switch” and“variable impeder” may be interchangeable. At least in part throughapplication of a critical voltage and a critical current between theterminals, such as between conductive terminals 101 and 103, a CEM, suchas material 102, may transition between aforementioned relativelyconductive/lower impedance states and relatively insulative/higherimpedance states. As mentioned, a CEM, such as one or more materials102, in a variable impeder device, such as CES device 100, maytransition between a first impedance state and a second impedance statedue to a quantum mechanical transition of the correlated electron switchmaterial as a result an applied critical voltage and an applied criticalcurrent, as described in more detail below. Also, as mentioned above, avariable impeder device, such as variable impeder device 100, mayexhibit properties of both variable resistance and variable capacitance.

FIG. 2 is a diagram showing an example voltage versus current densityprofile of a device formed from a CEM according to an embodiment 200.Based, at least in part, on a voltage applied to terminals of a CEMdevice, for example, during a “write operation,” a CEM device may beplaced into a relatively low-impedance state or a relativelyhigh-impedance state. For example, application of a voltage V_(set) anda current density J_(set) may place a CEM device into a relativelylow-impedance memory state. Conversely, application of a voltageV_(reset) and a current density J_(reset) may place a CEM device into arelatively high-impedance memory state. As shown in FIG. 2, referencedesignator 210 illustrates the voltage range that may separate V_(set)from V_(reset). Following placement of a CEM device into anhigh-impedance state or low-impedance state, the particular state of aCEM device may be detected by application of a voltage V_(read) (e.g.,during a read operation) and detection of a current or current densityat terminals of a CEM device.

According to an embodiment, a CEM device of FIG. 2 may include anytransition metal oxide (TMO), such as, for example, perovskites, Mottinsulators, charge exchange insulators, and Anderson disorderinsulators. In particular implementations, a CEM device may be formedfrom switching materials, such as nickel oxide, cobalt oxide, ironoxide, yttrium oxide, and perovskites, such as chromium doped strontiumtitanate, lanthanum titanate, and the manganate family includingpraseodymium calcium manganate, and praseodymium lanthanum manganite,just to provide a few examples. In particular, oxides incorporatingelements with incomplete “d” and “f” orbital shells may exhibitsufficient impedance switching properties for use in a CEM device. Otherimplementations may employ other transition metal compounds withoutdeviating from claimed subject matter.

In one aspect, a CEM device of FIG. 2 may comprise materials of thegeneral form AB:L_(x) (such as NiO:CO) where AB represents a transitionmetal, transition metal compound, or transition metal oxide variableimpedance material and L_(x) represents a dopant ligand; though itshould be understood that these are exemplary only and are not intendedto limit claimed subject matter. Particular implementations may employother variable impedance materials as well. Nickel oxide, NiO, isdisclosed as one particular TMO. NiO materials discussed herein may bedoped with extrinsic ligands, L_(x) which may establish and/or stabilizevariable impedance properties. In particular, NiO variable impedancematerials disclosed herein may include a carbon-containing ligand suchas carbonyl (CO), forming NiO:CO. In another particular example, NiOdoped with extrinsic ligands may be expressed as NiO:L_(x), where L_(x)is a ligand element or compound and x indicates a number of units of theligand for one unit of NiO. One skilled in the art may determine a valueof x for any specific ligand and any specific combination of ligand withNiO or any other transition metal compound simply by balancing valences.In particular, NiO variable impedance materials disclosed herein mayinclude carbon containing molecules of the form C_(a)H_(b)N_(d)O_(f) (inwhich a≧1, and b, d and f≧0) such as: carbonyl (CO), cyano (CN⁻),ethylene diamine (C₂H₈N₂), phen(1,10-phenanthroline) (C₁₂H₈N₂),bipyridine (C₁₀,H₈N₂), ethylenediamine ((C₂H₄(NH₂)₂), pyridine (C₅H₅N),acetonitrile (CH₃CN), and cyanosulfanides such as thiocyanate (NCS⁻),for example.

In accordance with FIG. 2, if sufficient bias is applied (e.g.,exceeding a band-splitting potential) and the aforementioned Mottcondition is satisfied (e.g., injected electron holes are of apopulation comparable to a population of electrons in a switchingregion, for example), a CEM device may switch from a relativelylow-impedance state to a substantially dissimilar impedance state, suchas a relatively high-impedance state, responsive to a Mott transition.This may correspond to point 208 of the voltage versus current densityprofile of FIG. 2. At, or suitably nearby this point, electrons are nolonger screened and become localized. This correlation may result in astrong electron-electron interaction potential which may operate tosplit the bands to form a relatively high-impedance material. If a CEMdevice comprises a relatively high-impedance state, current maygenerated by transportation of electron holes. Consequently, if athreshold voltage is applied across terminals of a CEM device, electronsmay be injected into a metal-insulator-metal (MIM) diode over thepotential barrier of the MIM device. If a threshold current of electronsis injected and a threshold potential is applied across terminals toplace a CEM device into a “set” state, an increase in electrons mayscreen electrons and remove a localization of electrons, which mayoperate to collapse the band-splitting potential, thereby bringing abouta relatively low-impedance state.

According to an embodiment, current in a CEM device may be controlled byan externally applied “compliance” condition, which may be determined atleast partially on the basis of an applied external current, which maybe limited during a write operation, for example, to place a CEM deviceinto a relatively high-impedance state. This externally-appliedcompliance current may, in some embodiments, also set a condition of acurrent density for a subsequent reset operation to place a CEM deviceinto a relatively high-impedance state. As shown in the particularimplementation of FIG. 2, a current density J_(comp) may be appliedduring a write operation at point 116 to place a CEM device into arelatively high-impedance state, may determine a compliance conditionfor placing a CEM device into a low-impedance state in a subsequentwrite operation. As shown in FIG. 2, a CEM device may be subsequentlyplaced into a low-impedance state by application of a current densityJ_(reset)≧J_(comp) at a voltage V_(reset) at point 208, at whichJ_(comp) is externally applied.

In embodiments, compliance may set a number of electrons in a CEM devicewhich may be “captured” by holes for the Mott transition. In otherwords, a current applied in a write operation to place a CEM device intoa relatively low-impedance memory state may determine a number of holesto be injected to a CEM device for subsequently transitioning a CEMdevice to a relatively high-impedance memory state.

As pointed out above, a reset condition may occur in response to a Motttransition at point 208. As pointed out above, such a Mott transitionmay bring about a condition in a CEM device in which a concentration ofelectrons n approximately equals, or becomes at least comparable to, aconcentration of electron holes p. This condition may be modeledaccording to expression (1) as follows:

$\begin{matrix}{{{\lambda_{TF}n^{\frac{1}{3}}} = {\left. C \right.\sim 0.26}}{n = \left( \frac{C}{\lambda_{TF}} \right)^{3}}} & (1)\end{matrix}$

In expression (1), λ_(TF) corresponds to a Thomas Fermi screeninglength, and C is a constant.

According to an embodiment, a current or current density in region 204of the voltage versus current density profile shown in FIG. 2, may existin response to injection of holes from a voltage signal applied acrossterminals of a CEM device. Here, injection of holes may meet a Motttransition criterion for the low-impedance state to high-impedance statetransition at current I_(MI) as a threshold voltage V_(MI) is appliedacross terminals of a CEM device. This may be modeled according toexpression (2) as follows:

$\begin{matrix}{{{I_{MI}\left( V_{MI} \right)} = {\frac{{dQ}\left( V_{MI} \right)}{dt} \approx \frac{Q\left( V_{MI} \right)}{t}}}{{Q\left( V_{MI} \right)} = {{qn}\mspace{11mu} \left( V_{MI} \right)}}} & (2)\end{matrix}$

Where Q(V_(MI)) corresponds to the charged injected (holes or electrons)and is a function of an applied voltage. Injection of electrons and/orholes to enable a Mott transition may occur between bands and inresponse to threshold voltage V_(MI), and threshold current I_(MI). Byequating electron concentration n with a charge concentration to bringabout a Mott transition by holes injected by I_(MI) in expression (2)according to expression (1), a dependency of such a threshold voltageV_(MI) on Thomas Fermi screening length λ_(TF) may be modeled accordingto expression (3), as follows:

$\begin{matrix}{{{I_{MI}\left( V_{MI} \right)} = {\frac{Q\left( V_{MI} \right)}{t} = {\frac{{qn}\mspace{11mu} \left( V_{MI} \right)}{t} = {\frac{q}{t}\left( \frac{C}{\lambda_{TF}} \right)^{3}}}}}{{J_{reset}\left( V_{MI} \right)} = {{J_{MI}\left( V_{MI} \right)} = {\frac{I_{MI}\left( V_{MI} \right)}{A_{CEM}} = {\frac{q}{A_{{CEM}^{1}}}\left( \frac{C}{\lambda_{TF}\left( V_{MI} \right)} \right)^{3}}}}}} & (3)\end{matrix}$

In which A_(CEM) is a cross-sectional area of a CEM device; andJ_(reset)(V_(MI)) may represent a current density through a CEM deviceto be applied to a CEM device at a threshold voltage V_(MI), which mayplace a CEM device in a relatively high-impedance state.

FIG. 3 depicts a schematic diagram of an equivalent circuit of anexample CEM switch device according to an embodiment 300. As previouslymentioned, a correlated electron device, such as a CEM switch, a CERAMarray, or other type of device utilizing one or more correlated electronmaterials may comprise variable or complex impedance device that mayexhibit characteristics of both variable resistance and variablecapacitance. In other words, impedance characteristics for a CEMvariable impedance device, such as the device according to embodiment300, may depend at least in part on resistance and capacitancecharacteristics of the device if measured across device terminals 301and 302, for example. In an embodiment, an equivalent circuit for avariable impedance device may comprise a variable resistor, such asvariable resistor 310, in parallel with a variable capacitor, such asvariable capacitor 320. Of course, although a variable resistor 310 andvariable capacitor 320 are depicted in FIG. 3 as comprising discretecomponents, a variable impedance device, such as device of embodiment300, may comprise a substantially homogenous CEM and claimed subjectmatter is not limited in this respect.

Table 1 below depicts an example truth table for an example variableimpedance device, such as the device of embodiment 300.

TABLE 1 Correlated Electron Switch Truth Table Resistance CapacitanceImpedance R_(high)(V_(applied)) C_(high)(V_(applied))Z_(high)(V_(applied)) R_(low)(V_(applied)) C_(low)(V_(applied))~0Z_(low)(V_(applied))

In an embodiment, Table 1 shows that a resistance of a variableimpedance device, such as the device of embodiment 300, may transitionbetween a low-impedance state and a substantially dissimilarhigh-impedance state as a function at least partially dependent on avoltage applied across a CEM device. In an embodiment, an impedanceexhibited at a low-impedance state may be approximately in the range of10.0-100,000.0 times lower than a substantially dissimilar impedanceexhibited in a high-impedance state. In other embodiments, an impedanceexhibited at a low-impedance state may be approximately in the range of5.0 to 10.0 times lower than an impedance exhibited in a high-impedancestate, for example. It should be noted, however, that claimed subjectmatter is not limited to any particular impedance ratios betweenhigh-impedance states and low-impedance states. Truth Table 1 shows thata capacitance of a variable impedance device, such as the device ofembodiment 300, may transition between a relatively lower capacitancestate, which, in an example embodiment, may comprise approximately zero,or very little, capacitance, and a relatively higher capacitance statethat is a function, at least in part, of a voltage applied across a CEMdevice.

According to an embodiment, a CEM device, which may be utilized to forma CEM switch, a CERAM memory device, and/or a variety of otherelectronic devices comprising one or more correlated electron materials,may be placed into a relatively low-impedance memory state, such as bytransitioning from a relatively high-impedance state, for example, viainjection of a sufficient quantity of electrons to satisfy a Motttransition criteria. In transitioning a CEM device to a relativelylow-impedance state, if enough electrons are injected and the potentialacross the terminals of a CEM device overcomes a threshold switchingpotential (e.g., V_(set)), injected electrons may begin to screen. Aspreviously mentioned, screening may operate to unlocalizedouble-occupied electrons to collapse the band-splitting potential,thereby bringing about a relatively low-impedance state.

In one or more embodiments, changes in impedance states of CEM devices,such as from a relatively low-impedance state to a substantiallydissimilar high-impedance state, for example, may be brought about bythe “back-donation” of electrons of compounds comprising Ni_(x):N_(y)(wherein the subscripts “x” and “y” comprise whole numbers). As the termis used herein, “back-donation” refers to a supplying of one or moreelectrons to a transition metal, transition metal oxide, or anycombination thereof, by an adjacent molecule of the lattice structure,for example, comprising the transition metal, transition metal oxide, orcombination thereof. Back-donation permits a transition metal,transition metal oxide, or combination thereof, to maintain anionization state that is favorable to electrical conduction under theinfluence of an applied voltage. In one or more embodiments,back-donation in a correlated electron material, for example, may occurresponsive to use of a dopant, such as carbonyl (CO), controllably andreversibly “donate” electrons to a conduction band of the transitionmetal or transition metal oxide, such as nickel, for example, duringoperation. Back-donation may be reversed, in a nickel oxide material,for example, (e.g., NiO:CO), which may thereby permit the nickel oxidematerial to switch to exhibiting a high-impedance property during deviceoperation. Thus, in this context, a back-donating material refers to amaterial that exhibits an impedance switching property, such asswitching from a first impedance state to a substantially dissimilarsecond impedance state (e.g., from a relatively low impedance state to arelatively high impedance state, or vice versa) based, at least in part,on influence of an applied voltage to control donation of electrons, andreversal of the electron donation, to and from a conduction band of thematerial.

In some embodiments, by way of back-donation, a CEM switch comprising atransition metal or a transition metal oxide, may exhibit low-impedanceproperties if the transition metal, such as nickel, for example, isplaced into an oxidation state of 2+ (e.g., Ni²⁺ in a material, such asNiO:CO). Conversely, electron back-donation may be reversed if thetransition metal, such as nickel, for example, is placed into anoxidation state of either 1+ or 3+. Accordingly, back-donation mayresult in “disproportionation,” which may comprise substantiallysimultaneous oxidation and reduction reaction, such as:

2Ni²⁺→Ni¹⁺+Ni³⁺  (4)

Such disproportionation, in this instance refers to formation of nickelions as Ni¹⁺ 30 Ni³⁺ as shown in expression (4), which may bring about,for example, a relatively high-impedance state during operation of a CEMdevice. In an embodiment, a carbon-containing ligand, such as a carbonylmolecule (CO), may permit sharing of electrons during operation of theCEM device so as to permit the disproportionation reaction and itsreversal:

Ni¹⁺+Ni³⁺→2Ni²⁺  (5)

As previously mentioned, reversal of the disproportionation reaction, asshown in expression (5), permits nickel-based CEM to return to arelatively low-impedance state, in one or more embodiment.

In one or more embodiments, depending on an atomic concentration ofcarbon in NiO:CO, for example, which may vary from values approximatelyin the range of an atomic percentage of 0.1% to 10.0%, V_(reset) andV_(set), as shown in FIG. 2, may vary approximately in the range of 0.1V to 10.0 V subject to the condition that V_(set)≧>V_(reset). Forexample, in one possible embodiment, V_(reset) may occur at a voltageapproximately in the range of 0.1 V to 1.0 V, and V_(set) may occur at avoltage approximately in the range of 1.0 V to 2.0 V, for example. Itshould be noted, however, that variations in V_(set) and V_(reset) mayoccur based, at least in part, on a variety of factors, such as atomicconcentration of a back-donating material, such as NiO:CO and othermaterials present in a CEM device, as well as other process variations,and claimed subject matter is not limited in this respect.

In certain embodiments, atomic layer deposition may be utilized to formfilms comprising nickel oxide materials, such as NiO:CO, to permitelectron back-donation during operation of the device in a circuitenvironment, for example, to give rise to a low-impedance state. Alsoduring operation in a circuit environment, for example, electronback-donation may be reversed so as to give rise to a high-impedancestate, for example. In particular embodiments, atomic layer depositionmay utilize two or more “precursor” sources to deposit components of,for example, NiO:CO, or other transition metal oxide, transition metalcompounds or combinations thereof, onto a conductive substrate. In anembodiment, layers of a CEM device may be deposited utilizing separatemolecules, AX and BY, according to expression (6), below:

AX _((gas)) +BY _((gas)) =AB _((solid)) +XY _((gas))   (6)

Wherein “A” of expression (6) corresponds to a transition metal,transition metal oxide, or any combination thereof. In embodiments, atransition metal oxide may comprise nickel, but may comprise othertransition metals and/or transition metal oxides, such as aluminum,cadmium, chromium, cobalt, copper, gold, iron, manganese, mercury,molybdenum, nickel palladium, rhenium, ruthenium, silver, tin, titanium,vanadium.

In particular embodiments, CEM compounds that comprise more than onetransition metal oxide may also be utilized, such as yttrium titanate(YTiO₃). “X” of expression (6) may comprise a ligand, such as organicligand, comprising amidinate (AMD), dicyclopentadienyl (Cp)₂,diethylcyclopentadienyl (EtCp)₂,Bis(2,2,6,6-tetramethylheptane-3,5-dionato) ((thd)₂), acetylacetonate(acac), bis(methylcyclopentadienyl) ((CH₃C₅H₄)₂), dimethylglyoximate(dmg)₂, 2-amino-pent-2-en-4-onato (apo)₂, (dmamb)₂ wheredmamb=1-dimethylamino-2-methyl-2-butanolate, (dmamp)2 wheredmamp=1-dimethylamino-2-methyl-2-propanolate,Bis(pentamethylcyclopentadienyl) (C₅(CH₃)₅)₂ and carbonyl (CO)₄.Accordingly, in some embodiments, nickel-based precursors AX maycomprise, for example, nickel amidinates (Ni(AMD)) an example of whichis Ni(MeC(NBu)₂)₂, nickel dicyclopentadienyl (Ni(Cp)₂), nickeldiethylcyclopentadienyl (Ni(EtCp)₂),Bis(2,2,6,6-tetramethylheptane-3,5-dionato)Ni(II) (Ni(thd)₂), nickelacetylacetonate (Ni(acac)₂), bis(methylcyclopentadienyl)nickel(Ni(CH₃C₅H4)₂, Nickel dimethylglyoximate (Ni(dmg)₂), Nickel2-amino-pent-2-en-4-onato (Ni(apo)₂), Ni(dmamb)₂ wheredmamb=1-dimethylamino-2-methyl-2-butanolate, Ni(dmamp)₂ wheredmamp=1-dimethylamino-2-methyl-2-propanolate,Bis(pentamethylcyclopentadienyl) nickel (Ni(C₅(CH₃)₅)₂, and nickelcarbonyl (Ni(CO)₄), just to name a few examples.

In expression (6), “BY” may comprise an oxidizer, such as oxygen (O₂),ozone (O₃), nitric oxide (NO), nitrous oxide (N₂O), hydrogen peroxide(H₂O₂), water (H₂O), just to name a few examples. In embodiments, the AXcompound may comprise a transition metal oxide or a transition metalcompound. BY may comprise a species chosen such that the reaction shownof expression (6) may form AB, wherein AB represents the CEM formed bythe process. In other embodiments, plasma may be used with an oxidizerto form oxygen radicals or other activated species to form the CEM. Inother embodiments, the CEM may be formed by chemical vapor deposition ofany type or by sputter deposition or by physical vapor deposition.Therefore, in some embodiments, the X and/or Y may not be required toform AB (such as in the case of sputtering from a target of AB or cosputtering from a target of A and a target of B, or sputtering from atarget of A in an ambient environment comprising B. It should be notedthat concentrations, such as atomic concentration, of precursor, such asAX and BY may be adjusted so as to bring about a final atomicconcentration of carbon, such as in the form of carbonyl, of betweenapproximately 0.1% and 10.0%. However, claimed subject matter is notnecessarily limited to the above-identified precursors and/orconcentrations. Rather, claimed subject matter is intended to embraceall such precursors utilized in atomic layer deposition, chemical vapordeposition, plasma chemical vapor deposition, sputter deposition,physical vapor deposition, hot wire chemical vapor deposition, laserenhanced chemical vapor deposition, laser enhanced atomic layerdeposition, rapid thermal chemical vapor deposition or the like,utilized in fabrication of CEM devices.

In particular embodiments, such as embodiments utilizing atomic layerdeposition, a substrate may be exposed to precursors in a heatedchamber, which may attain, for example, a temperature approximately inthe range of 20.0° C. to 1000.0° C., for example, or betweentemperatures approximately in the range of 20.0° C. and 500.0° C. incertain embodiments. In one particular embodiment, in which atomic layerdeposition of NiO:CO is performed, temperature ranges approximately inthe range of 20.0° C. and 400.0° C. may be utilized. After exposure toprecursor sources, such sources may be purged from the heated chamber,wherein purging may occur over durations approximately in the range of0.5 seconds to 180.0 seconds. It should be noted, however, that theseare merely examples of potentially suitable temperatures and exposuretimes, and claimed subject matter is not limited in this respect.

In certain embodiments, a single two-precursor cycle utilizing atomiclayer deposition may bring about a CEM device layer comprising athickness approximately in the range of 0.6 Å to 1.5 Å. Accordingly, inan embodiment, to form a CEM device film comprising a thickness ofapproximately 500 Å utilizing an atomic layer deposition process inwhich layers comprise a thickness of approximately 0.6 Å, 800-900two-precursor cycles, such as AX+BY of equation (6), for example, may beutilized. In another embodiment, utilizing an atomic layer depositionprocess in which layers comprise approximately 1.5 Å, 300 to 350two-precursor cycles, such as AX+BY, for example, may be utilized. Itshould be noted that atomic layer deposition may be utilized to form CEMdevice films having other thicknesses, such as thicknesses approximatelyin the range of 1.5 nm and 150.0 nm, for example, and claimed subjectmatter is not limited in this respect.

FIG. 4A shows a simplified flowchart for an example embodiment of amethod for fabricating correlated electron device materials according toan embodiment 400. Example implementations, such as described in FIGS.4A, 4B, and 4C, for example, may include blocks in addition to thoseshown and described, fewer blocks, or blocks occurring in an orderdifferent than may be identified, or any combination thereof. In anembodiment, a method may include blocks 410, 420, 430, 440 and/or 450,for example. An example embodiment of FIG. 4A may accord with thegeneral description of atomic layer deposition previously describedherein. The method of FIG. 4A may begin at block 210, which may compriseexposing a substrate, in a heated chamber, for example, to a firstprecursor in a gaseous state (e.g., “AX”), wherein the first precursorcomprises a transition metal oxide, a transition metal, a transitionmetal compound or any combination thereof, and a first ligand. Anexample embodiment may continue at block 420, which may compriseremoving the precursor AX and byproducts of AX by using an inert gas orevacuation or combination. An example embodiment may continue at block430, which may comprise exposing the substrate to a second precursor(e.g., BY) in a gaseous state, wherein the second precursor comprises aoxide so as to form a first layer of the film of a CEM device. Anexample embodiment may continue at block 440, which may compriseremoving the precursor BY and byproducts of BY through the use of aninert gas or evacuation or combination. An example embodiment maycontinue at block 450, which may comprise repeating the exposing of thesubstrate to the first and second precursors with intermediate purgeand/or evacuation steps so as to form additional layers of the filmuntil the correlated electron material is capable of exhibiting a ratioof first to second impedance states of at least 5.0:1.0.

FIG. 4B shows a simplified flowchart for an example embodiment of amethod for fabricating correlated electron device materials according toan embodiment 460. An example embodiment of FIG. 4B may accord with thegeneral description of chemical vapor deposition or CVD and/orvariations of CVD such as plasma enhanced CVD and/or others. In FIG. 4B,such as at block 460, a substrate may be exposed to precursor AX and BYsimultaneously under conditions of pressure and temperature to promotethe formation of Aft which corresponds to a CEM. Additional approachesmay be employed to bring about formation of a CEM, such as applicationof direct and/or remote plasma, use of hot wire to partially decomposeprecursors, and/or lasers to enhance reactions as examples of forms ofCVD. Example CVD film processes and/or variations may be employed for aduration and/or under conditions as can be determined by one skilled inthe art of CVD until, for example, correlated electron material havingappropriate thickness and exhibiting appropriate properties, such aselectrical properties, such as a ratio of first to second impedancestates of at least 5.0:1.0, may be formed.

FIG. 4C shows a simplified flowchart for an example embodiment 470 of amethod for fabricating correlated electron device materials. An exampleembodiment of FIG. 4C may accord with the general description ofphysical vapor deposition or PVD or Sputter Vapor Deposition orvariations of these and/or related embodiments. In FIG. 4C a substratemay be exposed in a chamber, for example, to an impinging stream ofprecursor having a “line of sight” under particular conditions oftemperature and pressure to promote formation of a CEM comprisingmaterial AB. A source of a precursor may be, for example, AB or A and Bfrom separate “targets” wherein deposition is brought about using astream of atoms or molecules that are physically or thermally or byother means removed (sputtered) from a target comprised of material A orB or AB and are in “line of sight” of the substrate in a process chamberwhose pressure is low enough or lower such that the mean free path ofthe atoms or molecules or A or B or AB is approximately or more than thedistance from the target to the substrate. A stream of AB (or A or B) orboth may combine to form AB on the substrate due to conditions of thereaction chamber pressure, temperature of the substrate and otherproperties that are controlled by one skilled in the art of PVD andsputter deposition. In other embodiments of PVD and/or sputterdeposition, the ambient environment may be a source such as BY or forexample an ambient of O₂ for the reaction of sputtered nickel to formNiO doped with carbon or CO, for example co-sputtered carbon. A PVD filmand its variations may continue for a time and under conditions as canbe determined by one skilled in the art of PVD until correlated electronmaterial of thickness and properties is deposited that is capable ofexhibiting a ratio of first to second impedance states of at least5.0:1.0, for example.

FIG. 5 is an illustration depicting a cross-sectional view of a portionof an example embodiment 500 of a correlated electron material device,in accordance with an embodiment. In an embodiment, a CEM device, suchas example embodiment 500, may include a CEM, such as CEM 520, formedbetween one or more electrodes, such as bottom electrode 510 and topelectrode 530, for example. In an embodiment, one or more electrodes,such as top electrode 530 and/or bottom electrode 510, may comprise asubstantially electrically conductive material, such as TiN, forexample, although claimed subject matter is not limited in scope in thisrespect. Also, in an embodiment, a CEM, such as CEM 520, may comprise aTMO material, such as example TMO materials previously mentioned.

In some circumstances, a relatively thin layer of a substantiallynon-conductive and/or insulative material, such as TiOx, for example,may develop in a region substantially adjacent to and/or part of anelectrode, such as 510 and/or 530, due at least in part to oxidation ofan electrode, such as 510 and/or 530. In some circumstances, suchoxidation may occur due at least in part to exposure of a CEM device,such as 500, to an oxidizing ambient, such as, for example, O₂, O₃, NO,N₂O, O⁺, NO₂, and/or H₂O, etc., and/or it may form at least in part dueto heat cycles such as a deposition process to form an electrode, suchas top electrode, 530, and oxygen from a CEM (for example NiO) oxidizingthe electrode (such as TiN), thereby forming a subtantiallynon-conductive interlayer, such as TiO_(x). Due at least in part to thedevelopment of the relatively thin layer of substantially non-conductiveand/or insulative material, electrical conductivity between theelectrode, such as 510 and/or 530, and a CEM, such as CEM 520, may bereduced, for example. Further, in at least some circumstances, therelatively thin layer of substantially non-conductive and/or insulativematerial, such as TiOx, may not switch impedance characteristics as onewould expect with a CEM, such as 520. This may, in at least somecircumstances, degrade the performance of a CEM device, such as 500, forexample.

To prevent, at least in part, development of a relatively thin layer ofsubstantially non-conductive and/or insulative material due at least inpart to oxidation of one or more electrodes, such as explained above, alayer of electrically conductive material, such as Ir, for example, maybe deposited and/or otherwise formed over an electrode, such as bottomelectrode 510, such that upon oxidation of an electrode, such as 510, aconductive metal oxide (CMO) material, such as IrO, may be formedbetween an electrode such as bottom electrode 510, and a CEM, such as520, as explained more fully below. Similarly, a layer of electricallyconductive material, such as Ir, for example, may be deposited and/orotherwise formed over a CEM, such as 520, prior to formation of anelectrode, such as top electrode 530, such that upon oxidation of anelectrode, such as 530, a conductive metal oxide (CMO) material, such as110, may be formed between an electrode, such as top electrode 530, anda CEM, such as 520, as also explained more fully below.

FIG. 6 is an illustration depicting a cross-sectional view of a portionof an example embodiment 600 of a CEM device including barrier layers,such as 615 and 625, at least in part to prevent formation of arelatively thin layer of substantially non-conductive and/or insulativematerial, such as TiO_(x), in a region substantially adjacent to and/orpart of one or more electrodes, such as bottom electrode 610 and/or topelectrode 630. For example, a bottom electrode, such as 610, maycomprise an electrically conductive material, such as TiN, for example,that may be deposited as an operation in a formation of ametal-insulator-metal (MIM) structure of a CEM device, such as CEMdevice 600, for example. A relatively thin layer of electricallyconductive material may be deposited and/or otherwise formed over anelectrode, such as 610, prior to depositing a CEM TMO material, such as620, to form a barrier layer, such as 615, that may, at least in part,prevent oxidation of an electrode, such as 610, and thereby preventformation of a layer of non-conductive and/or insulative and/ornon-CEM-like material, such as TiO_(x).

In an embodiment, example electrically conductive materials that may bedeposited and/or otherwise formed over an electrode, such as bottomelectrode 610, may include, for example, Iridium (Ir), Rhenium (Re),Ruthenium (Ru), Tungsten (W); titanium (Ti)metal oxides, metal carbides,metal oxynitrides, metal oxycarbides, and/or metal oxycarbinitride,although claimed subject matter is not limited in scope in this respect.Upon exposure of a CEM device, such as 600, to an oxidizing ambient,such as, for example, O₂, O₃, NO, N₂O, O⁺, NO₂, H₂O₂, and/or H₂O, etc.,a relatively thin layer of electrically conductive material, such as Ir,may form a conductive oxide, such as IrO₂, to produce a barrier layer,such as 615. Similarly, a relatively thin layer of electricallyconductive material, such as Re, may form a CMO material, such as ReO₃,and/or a relatively thin layer of electrically conductive material, suchas Ru, may form a CMO material, such as RuO₂, for example, to produce abarrier layer, such as 615. Again, claimed subject matter is not limitedin scope in these respects. Similarly, deposition and/or other formationof a CMO material, such as those mentioned above, for example, over aCEM, such as 620, prior to formation of an electrode, such as topelectrode 630, may produce a barrier layer, such as 625. In anembodiment, barrier layer 625 may comprise a CMO material including, forexample, IrO₂, ReO₃, and/or RuO₂, although again, claimed subject matteris not limited in scope in this respect. As mentioned, barrier layers615 and/or 625 may prevent, at least in part, oxidation of one or moreelectrodes 610 and/or 630, thereby preventing formation of one or morelayers of non-CEM-like and/or substantially non-conductive and/orinsulative materials in a region substantially adjacent to and/or partof one or more electrodes 610 and/or 630, in an embodiment.

In one or more embodiments, deposition and/or other formation of a CMOmaterial, such as to produce a barrier layer, such as 615 and/or 625,may occur as part of an electrode formation operation. Also, in one ormore embodiments, deposition and/or other formation of a CMO material,such as to produce a barrier layer, such as 615 and/or 625, may occur aspart of a stand-alone barrier layer formation operation. Further, in oneor more embodiments, deposition and/or other formation of a CMOmaterial, such as to produce a barrier layer, such as 615 and/or 625,may occur as part of a CEM material formation operation. Again, claimedsubject matter is not limited in scope in these respects.

In one or more embodiments, formation of a barrier layer, such as 625,comprising a CMO material, such as 110, may be advantageously employedbetween a CEM, such as 620, and an electrode, such as top electrode 630,at least in part due to potential annealing of a MIM stack, such as CEMdevice 600, in an oxidizing ambient in an effort to provide improvedperformance, such as healing etch damage, for example. Such an oxidizingannealing may promote oxidation between an electrode, such as topelectrode 630, and a CEM, such as 620, to form a relatively thin layerof non-CEM behaving insulative material unless a barrier layer, such as625, is formed between a CEM, such as 620, and an electrode, such as topelectrode 630, such as described above.

As utilized herein, the term “layer” and/or the like refers to one ormore materials deposited and/or otherwise formed on, over, under,beneath, and/or around one or more materials and/or structures in a CEMdevice, such as CEM device 600. Example layers may be deposited and/orotherwise formed of any of a wide range of materials and/or by any of awide range of processes and/or techniques, including those mentionedabove. Further, example layers may comprise any of a wide range ofthicknesses. For example, layers may have thicknesses ranging fromapproximately 1 Å-500 Å, in one or more embodiments. Also, in anembodiment, example barrier layers, such as 615, 625, 925, and/or 935,for example, may have thicknesses within a range of approximately 2 Å-50Å. Further, in an embodiment, a “relatively thin layer” may comprise alayer having a thickness within a range of approximately 2 Å-50 Å, forexample. Of course, claimed subject matter is not limited in scope tothe specific examples mentioned herein.

FIG. 7 depicts a simplified flowchart for an example embodiment 700 of aprocess for fabricating a CEM device, such as 600, including one or morebarrier layers at least in part to prevent oxidation of one or moreelectrodes, such as 610, in accordance with an embodiment. Exampleembodiments may include all of blocks 710-720, may include more thanblocks 710-720, and/or may include fewer than blocks 710-720. Further,the order of blocks 710-720 is merely an example order, and claimedsubject matter is not limited in scope in these respects.

At block 710, a layer of substantially conductive material, such as amaterial that may produce a CMO with exposure to an oxidizing ambient,for example, may be formed over an electrode, such as 610, prior toformation of a CEM, such as 620, at least in part to prevent oxidationof one or more electrodes, such as 610, and therefore to preventformation of a layer of a substantially non-conductive and/ornon-CEM-like material between an electrode, such as 610, and a CEM, suchas 620. In an embodiment, exposure of the layer of substantiallyconductive material to an oxidizing ambient may produce a barrier layer,such as 615, comprising a CMO, for example. Further, at block 720, aCEM, such as 620, may be deposited and/or otherwise formed over thelayer of substantially conductive material.

Similarly, although not depicted in example embodiment 700, a relativelythin layer of substantially conductive material that may form a barrierlayer, such as 625, may be formed and/or otherwise deposited over a CEM,such as 620, such as to prevent, at least in part, formation of a layerof substantially non-conductive material between an electrode, such astop electrode 630, and a CEM, such as CEM 620. In an embodiment, anelectrode, such as 630, may be formed and/or otherwise deposited over aCEM, such as CEM 620, for example. In this manner, in an embodiment,both top and bottom electrodes, such as 610 and 630, for example, may beprotected, at least in part, from oxidation, and/or from formation of asubstantially non-conductive layer between electrodes, such as 610 and630, and a CEM, such as CEM 620, for example.

FIG. 8 is an illustration depicting a cross-sectional view of a portionof an example embodiment 800 of a CEM device, in accordance with anembodiment. In an embodiment, a CEM device, such as example embodiment800, may include a CEM, such as CEM 830, formed between one or moreelectrodes, such as bottom electrode 820 and top electrode 840, forexample. In an embodiment, an electrode, such as bottom electrode 820,may be formed and/or otherwise deposited over a substrate, such as 810,in an embodiment. In an embodiment, one or more electrodes, such as topelectrode 840 and/or bottom electrode 840, may comprise a substantiallyelectrically conductive material, such as TiN, for example, althoughclaimed subject matter is not limited in scope in this respect. Also, inan embodiment, a CEM, such as CEM 830, may comprise a TMO material, suchas example TMO materials previously mentioned.

In some circumstances, CEM TMO materials, such as NiO, VO, TiO, and/orothers, for example, when doped with Carbon (C), and/or Carbonyl (CO)may behave as correlated electron materials, in that the impedancecharacteristics of the material may change with current and/or voltagein a substantially bulk fashion. In one or more embodiments, C and/or COmay comprise dopants in a CEM film, for example, and in some embodimentsrelatively high dopant amounts, such as from <0.1% to 10%, for example,may be employed. In one or more embodiments, C and/or CO, for example,may contribute to CEM impedance bulk-switching characteristics.

In some circumstances, following deposition and/or other formation of aCEM, such as 830, an electrode, such as 840, and/or other layers ofmaterials, such as metal layers, for example, may be formed, which mayinvolve application of heat. In some circumstances, application of heatto a CEM with C and/or CO dopants may result in diffusion of the Cand/or CO, for example. C and/or CO dopants are depicted in the exampleillustration of FIG. 8 as elements 850. As depicted in FIG. 8, C and/orCO dopants 850 may diffuse into one or more electrodes, such as 820and/or 850. In some circumstances, loss of C and/or CO dopant in a CEM,such as CEM 830, may result in altered and/or reduced performance of aCEM. Further, in some circumstances, diffusion of C and/or CO 850, forexample, into one or more electrodes, such as 820 and/or 840 mayincrease resistivity of the electrodes, thereby potentially negativelyimpacting performance of a CEM device, such as CEM device 800.

FIG. 9 is an illustration depicting a cross-sectional view of a portionof an example embodiment 900 of a CEM device including barrier layers,such as 925 and/or 935, at least in part to prevent C and/or CO 850diffusion from a CEM, such as CEM 830, in accordance with an embodiment.In an embodiment, to prevent, at least in part, diffusion of C and/or COdiffusion from a CEM, such as CEM 830, into one or more electrodes, suchas 820 and/or 840, one or more relatively thin, conductive layers may bedeposited and/or otherwise formed between one or more electrodes, suchas 820 and/or 840, and a CEM, such as 830, to produce one or morebarrier layers, such as 925 and/or 935. Example materials that may bedeposited and/or otherwise formed to produce one or more barrier layers,such as 925 and/or 935, may include, but are not limited to, TiN, TiCN,TiON, RuON, ReOxNy, ReO₃, RuO₂, WN, and/or IrO₂, for example. Examplecharacteristics for materials that may be employed in barrier layers,such as 925 and/or 935, may include relatively low resistivity andability to act as barriers to C and/or CO 850, in an embodiment.

In an embodiment, a barrier layer, such as 925, may be deposited and/orotherwise formed prior to deposition and/or other formation of a CEM,such as CEM 830, and another barrier layer, such as 935, may bedeposited and/or otherwise formed over a CEM, such as CEM 830. In anembodiment, one or more barrier layers, such as 925 and/or 935, may bedeposited and/or otherwise formed at least in part via atomic layerdeposition (ALD), chemical vapor deposition (CVD), and/or physical vapordeposition (PVD), and/or plasma enhanced versions of the aforementioned,although claimed subject matter is not limited in scope in this respect.

FIG. 10 is an illustration depicting a cross-sectional view of a portionof an example embodiment 1000 of a CEM device including barrier layers,such as 925 and/or 935, at least in part to prevent C and/or CO 850diffusion from a CEM, such as CEM 830, in accordance with an embodiment.As depicted in FIG. 10, for example embodiment 1000 of a CEM device, astack comprising a bottom electrode, such as 820, a CEM, such as 830,and a top electrode, such as 840, may be etched. In an embodiment, abarrier layer and/or film, such as 1060, may be deposited and/orotherwise formed via a conformal technique, such as via ALD, forexample, to deposit a barrier layer, such as 1060, on the edges of theetched stack to prevent, at least in part, out diffusion of C and/or CO850 from the edges. Additionally, in an embodiment, a barrier layer,such as 1060, may protect, at least in part, the edges of the etchedstack, for example. In an embodiment, a device side wall barrier mayalso be deposited before the bottom electrode in situations in which aCEM device may be integrated into an existing trench, hole, and/or otherfeature having existing walls, for example.

FIG. 11 depicts a simplified flowchart for an example embodiment 1100 ofa process for fabricating correlated electron material devices includingone or more barrier layers at least in part to prevent C and/or COdiffusion, for example, from a CEM, such as 830, in accordance with anembodiment. Example embodiments may include all of blocks 1110-1120, mayinclude more than blocks 1110-1120, and/or may include fewer than blocks1110-1120. Further, the order of blocks 1110-1120 is merely an exampleorder, and claimed subject matter is not limited in scope in theserespects.

At block 1110, in an embodiment, a relatively thin layer ofsubstantially conductive material, such as TiN, for example, may beformed over an electrode, such as 820, to prevent, at least in part,diffusion of C and/or CO from a CEM, such as CEM 830, into theelectrode, such as 820. Further, as depicted at block 1120, a CEM, suchas CEM 830, may be formed over a the layer of substantially conductivematerial, in an embodiment. In an embodiment, a carbon diffusion barrierlayer, such as 935, may comprise the same layer as an oxidation barrierlayer, such as 615, and/or it may comprise an additional layer. This is,in an embodiment, a CEM device may include one or more carbon diffusionbarrier layers, such as 925, and/or one or more oxidation barrierlayers, such as 615, and/or may include one or more barrier layersproviding both prevention of carbon diffusion and oxidation, forexample.

In an embodiment, the relatively thin layer of substantiallyelectrically conductive material may comprise a barrier layer, such as925, for example. Similarly, although not depicted in example embodiment1100, a relatively thin layer of substantially conductive material maybe formed and/or otherwise deposited over a CEM, such as 830, to form abarrier layer, such as 935, for example, such as to prevent, at least inpart, diffusion of C and/or CO, such as 850, from a CEM, such as 830,into an electrode, such as 840, that may be formed over a CEM, such asCEM 830. In this manner, in an embodiment, barrier layers 925 and 935both may prevent diffusion of C and/or CO, such as 850, from diffusionfrom a CEM, such as CEM 830, into one or more of electrodes 820 and/or840, for example.

In an embodiment, an example method may comprise forming a layer ofsubstantially conductive material between an electrode and a correlatedelectron material to prevent, at least in part, carbon diffusion fromthe correlated electron material into the electrode. Further, in anembodiment, the substantially conductive material may comprise one ormore of TiN, TiCN, TiON, RuON, ReOxNy, ReO₃, RuO₂, WN, or IrO₂, or anycombination thereof, for example. Additionally, in an embodiment, thecorrelated electron material may comprise a transition metal oxide dopedwith carbon. In an embodiment, the transition metal oxide may compriseone or more of NiO, VO, and/or TiO, or any combination thereof, forexample. Also, in an embodiment, dopant amounts, such as for carbon, forexample, may range from approximately less than 0.1% to approximately10%, for example.

Further, in an embodiment, an example method may further compriseforming a second layer of substantially conductive material between thecorrelated electron material and a second electrode to prevent carbondiffusion from the correlated electron material into the secondelectrode.

In an embodiment, an apparatus may comprise a layer of substantiallyconductive material positioned between an electrode and a correlatedelectron material to prevent carbon diffusion from the correlatedelectron material into the electrode. Further, in an embodiment, thesubstantially conductive material may comprise one or more of TiN, TiCN,TiON, RuON, ReOxNy, ReO₃, RuO₂, WN, or

IrO₂, or any combination thereof, for example. Additionally, in anembodiment, the correlated electron material may comprise a transitionmetal oxide doped with carbon. Also, in an embodiment, the transitionmetal oxide may comprise one or more of NiO, VO, and/or TiO, or anycombination thereof, for example, and dopant amounts, such as forcarbon, for example, may range from approximately less than 0.1% toapproximately 10%, for example.

Additionally, in an embodiment, the apparatus may further comprise asecond layer of substantially conductive material positioned between thecorrelated electron material and a second electrode to prevent, at leastin part, carbon diffusion from the correlated electron material into thesecond electrode.

In an embodiment, an example process may include forming a layer ofsubstantially conductive material between an electrode and a correlatedelectron material to prevent correlated electron material dopant such ascarbon from diffusing out of the correlated electron material. In anexample embodiment, the substantially conductive material may comprise asubstantially conductive metal oxide, metal nitride, or metal carbide,or any combination thereof.

Further, in an embodiment, a forming of a layer of substantiallyconductive material over an electrode may comprise depositing a layer ofmetal material over the electrode and exposing the metal material to anoxidizing ambient material to produce, at least in part, a substantiallyconductive metal oxide, metal carbide, metal oxynitride, metaloxycarbide, or metal oxycarbinitride, or any combination thereof. In anembodiment, a metal material may comprise Ir, Re, W, Ti or Ru, or anycombination thereof. Additionally, in an embodiment, a substantiallyconductive metal oxide may comprise IrO_(x)N_(y)C_(z),ReO_(x)N_(y)C_(z), RuO_(x)N_(y)C_(z), WO_(x)N_(y)C_(z), orTiO_(x)N_(y)C_(z), (x, y, and z≧0), or any combination thereof. Further,in an embodiment, an oxidizing ambient material may comprise O₂, O₃, NO,N₂O, O*, NO₂, H₂O₂ or H₂O, or any combination thereof.

Also, in an embodiment, an example process may include forming a secondlayer of substantially conductive material over a correlated electronmaterial and forming a second electrode over the second layer ofsubstantially conductive material, wherein the second layer ofsubstantially conductive material prevents correlated electron materialdopant, such as carbon, from diffusing out of the CEM.

In an additional embodiment, an apparatus may comprise a layer ofsubstantially conductive material positioned on an electrode to carbondiffusion out of the CEM and a correlated electron material positionedover the layer of substantially conductive material. A substantiallyconductive material may comprise a substantially conductive metal oxide,in an embodiment. Also, in an embodiment, a substantially conductivemetal oxide material may comprise a metal material to be exposed to anoxidizing ambient material, wherein the metal material may include Ir,Re, W, Ti or Ru, or any combination thereof, for example. Additionally,substantially conductive metal oxide may comprise IrO_(x)N_(y)C_(z),ReO_(x)N_(y)C_(z), RuO_(x)N_(y)C_(z), WO_(x)N_(y)C_(z), orTiO_(x)N_(y)C_(z), (x, y, z≧0), or any combination thereof. In anembodiment, an oxidizing ambient material may include O₂, O₃, NO, N₂O,O⁺, NO₂, H₂O₂ or H₂O, or any combination thereof.

Further, in an embodiment, an apparatus may further include a secondlayer of substantially conductive material positioned over thecorrelated electron material and a second electrode positioned over thesecond layer of substantially conductive material, wherein the secondlayer of substantially conductive material to prevent diffusion of adopant out of a correlated electron material.

An additional embodiment may include a layer of substantially conductivematerial disposed between an electrode and a correlated electronmaterial, wherein the substantially conductive material comprises asubstantially conductive metal compound to prevent, at least in part,diffusion of a dopant out of a correlated electron material. In anembodiment, a substantially conductive metal compound material may comein contact with a CEM dopant layer and/or may be subsequently exposed toprocesses that may otherwise result in diffusion of the CEM dopant outof the CEM film into the electrode. In an embodiment, a metal compoundmaterial may include Ir, Re, W, Ti, or Ru, or any combination thereof.Also, in an embodiment, a substantially conductive metal oxide maycomprise IrO_(x)N_(y)C_(z), ReO_(x)N_(y)C_(z), RuO_(x)N_(y)C_(z),WO_(x)N_(y)C_(z), or TiO_(x)N_(y)C_(z), (x, y, z≧0), or any combinationthereof. Of course, claimed subject matter is not limited in scope inthese respects.

In the context of the present disclosure, the term “connection,” theterm “component” and/or similar terms are intended to be physical, butare not necessarily always tangible. Whether or not these terms refer totangible subject matter, thus, may vary in a particular context ofusage. As an example, a tangible connection and/or tangible connectionpath may be made, such as by a tangible, electrical connection, such asan electrically conductive path comprising metal or other electricalconductor, that is able to conduct electrical current between twotangible components. Likewise, a tangible connection path may be atleast partially affected and/or controlled, such that, as is typical, atangible connection path may be open or closed, at times resulting frominfluence of one or more externally derived signals, such as externalcurrents and/or voltages, such as for an electrical switch. Non-limitingillustrations of an electrical switch include a transistor, a diode,etc. However, a “connection” and/or “component,” in a particular contextof usage, likewise, although physical, can also be non-tangible, such asa connection between a client and a server over a network, whichgenerally refers to the ability for the client and server to transmit,receive, and/or exchange communications.

In a particular context of usage, such as a particular context in whichtangible components are being discussed, therefore, the terms “coupled”and “connected” are used in a manner so that the terms are notsynonymous. Similar terms may also be used in a manner in which asimilar intention is exhibited. Thus, “connected” is used to indicatethat two or more tangible components and/or the like, for example, aretangibly in direct physical contact. Thus, using the previous example,two tangible components that are electrically connected are physicallyconnected via a tangible electrical connection, as previously discussed.However, “coupled,” is used to mean that potentially two or moretangible components are tangibly in direct physical contact.Nonetheless, is also used to mean that two or more tangible componentsand/or the like are not necessarily tangibly in direct physical contact,but are able to co-operate, liaise, and/or interact, such as, forexample, by being “optically coupled.” Likewise, the term “coupled” maybe understood to mean indirectly connected in an appropriate context. Itis further noted, in the context of the present disclosure, the termphysical if used in relation to memory, such as memory components ormemory states, as examples, necessarily implies that memory, such memorycomponents and/or memory states, continuing with the example, istangible.

Additionally, in the present disclosure, in a particular context ofusage, such as a situation in which tangible components (and/orsimilarly, tangible materials) are being discussed, a distinction existsbetween being “on” and being “over.” As an example, deposition of asubstance “on” a substrate refers to a deposition involving directphysical and tangible contact without an intermediary, such as anintermediary substance (e.g., an intermediary substance formed during anintervening process operation), between the substance deposited and thesubstrate in this latter example; nonetheless, deposition “over” asubstrate, while understood to potentially include deposition “on” asubstrate (since being “on” may also accurately be described as being“over”), is understood to include a situation in which one or moreintermediaries, such as one or more intermediary substances, are presentbetween the substance deposited and the substrate so that the substancedeposited is not necessarily in direct physical and tangible contactwith the substrate.

A similar distinction is made in an appropriate particular context ofusage, such as in which tangible materials and/or tangible componentsare discussed, between being “beneath” and being “under.” While“beneath,” in such a particular context of usage, is intended tonecessarily imply physical and tangible contact (similar to “on,” asjust described), “under” potentially includes a situation in which thereis direct physical and tangible contact, but does not necessarily implydirect physical and tangible contact, such as if one or moreintermediaries, such as one or more intermediary substances, arepresent. Thus, “on” is understood to mean “immediately over” and“beneath” is understood to mean “immediately under.”

It is likewise appreciated that terms such as “over” and “under” areunderstood in a similar manner as the terms “up,” “down,” “top,”“bottom,” and so on, previously mentioned. These terms may be used tofacilitate discussion, but are not intended to necessarily restrictscope of claimed subject matter. For example, the term “over,” as anexample, is not meant to suggest that claim scope is limited to onlysituations in which an embodiment is right side up, such as incomparison with the embodiment being upside down, for example. Anexample includes a flip chip, as one illustration, in which, forexample, orientation at various times (e.g., during fabrication) may notnecessarily correspond to orientation of a final product. Thus, if anobject, as an example, is within applicable claim scope in a particularorientation, such as upside down, as one example, likewise, it isintended that the latter also be interpreted to be included withinapplicable claim scope in another orientation, such as right side up,again, as an example, and vice-versa, even if applicable literal claimlanguage has the potential to be interpreted otherwise. Of course,again, as always has been the case in the specification of a patentapplication, particular context of description and/or usage provideshelpful guidance regarding reasonable inferences to be drawn.

Unless otherwise indicated, in the context of the present disclosure,the term “or” if used to associate a list, such as A, B, or C, isintended to mean A, B, and C, here used in the inclusive sense, as wellas A, B, or C, here used in the exclusive sense. With thisunderstanding, “and” is used in the inclusive sense and intended to meanA, B, and C; whereas “and/or” can be used in an abundance of caution tomake clear that all of the foregoing meanings are intended, althoughsuch usage is not required. In addition, the term “one or more” and/orsimilar terms is used to describe any feature, structure,characteristic, and/or the like in the singular, “and/or” is also usedto describe a plurality and/or some other combination of features,structures, characteristics, and/or the like. Furthermore, the terms“first,” “second” “third,” and the like are used to distinguishdifferent aspects, such as different components, as one example, ratherthan supplying a numerical limit or suggesting a particular order,unless expressly indicated otherwise. Likewise, the term “based on”and/or similar terms are understood as not necessarily intending toconvey an exhaustive list of factors, but to allow for existence ofadditional factors not necessarily expressly described.

Furthermore, it is intended, for a situation that relates toimplementation of claimed subject matter and is subject to testing,measurement, and/or specification regarding degree, to be understood inthe following manner. As an example, in a given situation, assume avalue of a physical property is to be measured. If alternativelyreasonable approaches to testing, measurement, and/or specificationregarding degree, at least with respect to the property, continuing withthe example, is reasonably likely to occur to one of ordinary skill, atleast for implementation purposes, claimed subject matter is intended tocover those alternatively reasonable approaches unless otherwiseexpressly indicated. As an example, if a plot of measurements over aregion is produced and implementation of claimed subject matter refersto employing a measurement of slope over the region, but a variety ofreasonable and alternative techniques to estimate the slope over thatregion exist, claimed subject matter is intended to cover thosereasonable alternative techniques, even if those reasonable alternativetechniques do not provide identical values, identical measurements oridentical results, unless otherwise expressly indicated.

It is further noted that the terms “type” and/or “like,” if used, suchas with a feature, structure, characteristic, and/or the like, using“optical” or “electrical” as simple examples, means at least partiallyof and/or relating to the feature, structure, characteristic, and/or thelike in such a way that presence of minor variations, even variationsthat might otherwise not be considered fully consistent with thefeature, structure, characteristic, and/or the like, do not in generalprevent the feature, structure, characteristic, and/or the like frombeing of a “type” and/or being “like,” (such as being an “optical-type”or being “optical-like,” for example) if the minor variations aresufficiently minor so that the feature, structure, characteristic,and/or the like would still be considered to be predominantly presentwith such variations also present. Thus, continuing with this example,the terms optical-type and/or optical-like properties are necessarilyintended to include optical properties. Likewise, the termselectrical-type and/or electrical-like properties, as another example,are necessarily intended to include electrical properties. It should benoted that the specification of the present disclosure merely providesone or more illustrative examples and claimed subject matter is intendedto not be limited to one or more illustrative examples; however, again,as has always been the case with respect to the specification of apatent application, particular context of description and/or usageprovides helpful guidance regarding reasonable inferences to be drawn.

1-19. (canceled)
 20. A method, comprising: forming a layer ofsubstantially conductive material between an electrode and a correlatedelectron material to prevent diffusion of a dopant from the correlatedelectron material.
 21. The method of claim 20, wherein the dopantcomprises carbon.
 22. The method of claim 20, wherein the forming thelayer of substantially conductive material to prevent diffusion of thedopant from the correlated electron material comprises forming the layerof substantially conductive material to prevent diffusion of the dopantfrom the correlated electron material into the electrode.
 23. The methodof claim 20, wherein the substantially conductive material comprises oneor more of TiN, TiCN, TiON, RuON, ReOxNy, ReO₃, RuO₂, WN, or IrO₂, orany combination thereof.
 24. The method of claim 20, wherein thecorrelated electron material comprises a transition metal oxide dopedwith carbon.
 25. The method of claim 20, further comprising: forming asecond layer of substantially conductive material between the correlatedelectron material and a second electrode to prevent diffusion of thedopant from the correlated electron material into the second electrode.26. The method of claim 20, wherein the layer of substantiallyconductive material comprises a thickness of no more than 50 Å.
 27. Anapparatus, comprising: a layer of substantially conductive materialpositioned between an electrode and a correlated electron material toprevent diffusion of a dopant from the correlated electron material. 28.The apparatus of claim 27, wherein the dopant to comprise carbon. 29.The apparatus of claim 27, wherein the layer of substantially conductivematerial to prevent diffusion of the dopant into the electrode.
 30. Theapparatus of claim 27, wherein the substantially conductive material tocomprise one or more of TiN, TiCN, TiON, RuON, ReOxNy, ReO₃, RuO₂, WN,or IrO₂, or any combination thereof.
 31. The apparatus of claim 27,wherein the correlated electron material to comprise a transition metaloxide doped with carbon, and wherein the layer of substantiallyconductive material to prevent diffusion of the carbon into theelectrode.
 32. The apparatus of claim 27, wherein the layer ofsubstantially conductive material to comprise a thickness of no morethan 50 Å.
 33. The apparatus of claim 27, further comprising: a secondlayer of substantially conductive material positioned between thecorrelated electron material and a second electrode to prevent diffusionof the dopant from the correlated electron material into the secondelectrode.
 34. A layer disposed between an electrode and a correlatedelectron material, comprising: a substantively conductive material toinclude one or more of TiN, TiCN, TiON, RuON, ReOxNy, ReO₃, RuO₂, WN, orIrO₂, or any combination thereof, to prevent diffusion of a dopant fromthe correlated electron material.
 35. The layer of claim 34, wherein thedopant to comprise carbon.
 36. The layer of claim 34, wherein the layerof substantially conductive material to prevent diffusion of the dopantinto the electrode.
 37. The layer of claim 34, wherein the correlatedelectron material to comprise a transition metal oxide doped withcarbon.
 38. The layer of claim 34, wherein the substantially conductivematerial to comprise a thickness of no more than 50 Å.